A collection can be defined as a group of related items that
can be referred to as a single unit. The System.Collections namespace provides
you with many classes and interfaces. Some of them are - ArrayList, List,
Stack, ICollection, IEnumerable, and IDictionary. Generics provide the
type-safety to your class at the compile time. While creating a data structure,
you never need to specify the data type at the time of declaration. The
System.Collections.Generic namespace contains all the generic collections.